1. Field of the Invention
The present invention relates generally to devices for driving cylindrical foundation support elements into the ground by means of a helical drive structure, and in particular to a method and apparatus for driving a cylindrical foundation support into the ground through the use of an installation drive component having respective guide and driving helices, which is releasably attached and inserted into the cylindrical foundation support and may be withdrawn from it following insertion thereof to the desired depth, so that the installation drive component may be used repeatedly for the same purpose.
2. Discussion of the Prior Art
It is known to provide a cylindrical foundation support element having an open lower end and which may be rotatably driven into the ground by virtue of the provision of an integral annular helix permanently affixed to the outer surface of the lower end of the support. The helix has an earth penetrating edge, and in conjunction with the cylindrical foundation defines an opening through which soil is allowed to pass into the chamber formed by the cylindrical wall of the foundation support. The opposite end of the cylindrical foundation support is adapted for releasable locking engagement to a drive element, which is used to rotate the support in a given direction, thus driving the support into the ground to a desired depth.
The existing cylindrical foundation supports of the type above described have several shortcomings. As mentioned, such supports are presently of a standard length, in part due to the manufacturing costs associated with constructing the support with an integral drive helix. This fact limits the use of such supports, to the extent that they are not always adapted to the particular soil conditions that may be encountered.
A second disadvantage manifested in the known examples is that the incorporation of the helix with the foundation support means that the combination may only be used once. That is, the potential value of the drive helix, which might be used repeatedly for such applications, is entirely lost because the helix is essentially disposed of by remaining buried with the support.
Another problem with such known structures is the cost that must be built into the price of such supports and which is directly attributable to the inclusion of a fixed felical drive member. Considerable cost savings may be realized from the manufacture of more simple cylindrical foundation supports that have no fixed drive helix.